I went for E

If it is btw C and D then D>C...both looked out of scope for me.
Kindly clarify

Wat is d right answer?
i went for A.
since it shows that diatom is independent of increase in rate of ferrous materials...

IMO A:

A: If algae has remained largely unchanged since the last ice age that mena sthere is no relevance between the quatity of ferrous materials present and algae growth.But the argument con cludes by saying that ferrous material promoted the increase in algae.
This is a direct attck on the conclusion of the argument.

B: The statement is talking about present scenario and actually supports the conclusion.

C: Presence of other materials has no relevance to realtionship between ferrous materials and algae .

D: Very ambigous answer. Can be eliminated.

E: This actually strengthens the argument. It states that if algae is not not harmed by ferrous matetial then ferrous materials can either remain neutral or promote algae growth.

IMO D

psg breakdown
conc: the hypothesis that he ferrous material, which was contained in atmospheric dust, had promoted a great increase in the population of Antarctica algae such as diatoms.
evidence :large amt of ferrous material and less CO2+ scientist reporting algae absorb carbon dioxide from the atmosphere

the assumption has been made that the low level of CO2 was a result of diatoms absorbing the gas and there was no other explanation for it

A) Diatoms are a microscopic form of algae that has remained largely unchanged since the last ice age
(in a way supports as then current analysis can result in similar findings)
(B) Computer models suggest that a large increase in ferrous material today could greatly promote the growth of oceanic algae.(unrelated/distorted ans as large amt of CO2 would increase such chances not ferrous material)
(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material.(other material not an issue here)
(E) Algae that currently grow in the oceans near Antarctica do not appear to be harmed by even a large increase in exposure to ferrous material. (so what even in previous time the ferrous material was available in large amounts but doesn't mention any reln with the diatoms growth)

(D) Sediment from the ocean floor near Antarctica reflects no increase, during the last ice age, in the rate at which the shells that diatoms leave when they die accumulated.
correct ans as if this idea is true and the shells don't show a huge change it rate...it casts doubt on the conclusion that diatoms are in huge no.